In IE go to Tools...Internet Options...Security tab, and set the Internet Zone level to "High". You can also click the Custom button and choose each setting individually. However, this won't get all the nasties out there that can hijack your system. I would recommend getting Ad-Aware, Spybot Search & Destroy, BHO Demon and/or Hijack Blaster, plus having a good anti-virus program that has an auto-protect feature that's always on and with updated-frequently virus definitions.
